Sol−Gel Preparation of PDMS/Silica Hybrid Antireflective Coatings with Controlled Thickness and Durable Antireflective Performance

Abstract

Thick silica antireflective (AR) coatings with controlled thickness and durable AR performance were prepared by a base-catalyzed sol-gel process using tetraethyl orthosilicate (TEOS) as precursor and hydroxyl-terminated polydimethylsiloxane (PDMS) as a modifier. The addition of PDMS greatly increased the controllable viscosity range of the silica sol but did not obviously affect the particle size. This phenomenon is attributed to a "compulsive aggregation" process of the sol, which involves the formation of "PDMS bridges" between silica particles in the sol. The mechanism of "PDMS bridge" formation is proposed based on sol viscosity, sol particle size changes, and FTIR identification. The increased controllable viscosity range provided a convenient way to prepare AR coatings with controlled thickness and therefore with controlled wavelength of maximum transmittance. The introduction of PDMS into the silica sol also increased the hydrophobicity and hence the durability of the AR coatings in wet environments.

PDMS-SiO2-TiO2-CaO hybrid materials – Cytocompatibility and nanoscale surface features

“…These results agree with the assumption that longer PDMS chains link silica domains, creating a hydrophobic surface as confirmed by NMR and SAXS measurements, also in agreement with a structural model proposed by Zhang et al [52,51] where PDMS chains act as bridges between the surface of silica nano particles. …”

Preparation of antireflective coatings with high transmittance and enhanced abrasion-resistance by a base/acid two-step catalyzed sol–gel process

“…It is known that the hydrophobic property of AR coatings is controlled by both surface chemical composition and surface topology [21]. The hydrophobicity of AR coatings can be obviously increased by increasing the film surface roughness [22,23]. However, the increase of surface roughness will result in surface light scattering which should be avoided for AR coatings used in optical parts.…”

An efficient way to prepare hydrophobic antireflective SiO2 film by sol–gel method

“…In the optical system of many fields like high power lasers, solar cells, solar collectors and so on, a large amount of energy can be lost because of the reflection on the glass surface [3,4] . The antireflective film on glass prepared by sol-gel method with many advantages like low reflection, high transmittance and high resistance to damage threshold have aroused wide spread attention and a lot of research [5][6][7] . However, on the process of forming antireflective film, the surface can be easily left many -OH groups, resulting in strong hydrophilicity, so that it tends to absorb water molecules in the air, and then bring down the transmittance [8] .…”